In recent years, in order to achieve device miniaturization, display devices in which the display unit and the input unit are integrally formed are in wide use. In recent years, in mobile devices such as mobile phones, PDAs (personal digital assistants), and laptop computers, display devices including touch panels that can detect a position of contact when a finger or an input stylus (object to be detected) comes into contact with the display surface are in wide use.
Touch panels of various types such as the conventional so-called resistive film (pressure-sensitive) type and capacitive type are known. Among these, touch panels of the capacitive type are in wide use.
In capacitive touch panels, a position of contact is detected by detecting changes in capacitance when a finger or an input stylus comes into contact with the display surface. Thus, it is possible to detect the position of contact by a simple operation.
Also, in capacitive touch panels, there is no need to provide two conductive films with an air layer therebetween as used in a resistive film touch panel, and thus, no boundary face reflection of external light, which would occur between the air layer and the conductive films, occurs.
However, because capacitive touch panels detect positions of contact by detecting changes in capacitance, if the touch panel receives external noise, there is a possibility that the lines of electric force change due to this noise, which causes the position of contact to not be accurately detected.
Conventionally, as touch panels, out-cell or on-cell type touch panels that are installed outside of the display panel have been widely used.
However, if the touch panel is provided on the outside of the display panel, then when performing touch panel operations while performing display, then the display panel generates radiation noise, which poses the problem of increasing the amount of noise received by the touch panel.
Thus, when providing the touch panel outside of the display panel, the S/N ratio (signal to noise ratio) decreases, which results in the detection accuracy of the touch panel decreasing, thus posing the risk of inaccurate detection of the position of contact.
Also, if the touch panel is provided on the outside of the display panel, then as a result of stacking the touch panel on the display panel, the thickness and weight of the device as a whole increases.
Furthermore, as a result of the touch panel being mounted on the outside of the display panel, external light is reflected not only at the surface of the touch panel but also at the boundary face between the touch panel and the display panel, which has a negative effect on contrast and visibility. Also, due to the touch panel being mounted on the outside of the display panel, the visibility decreases due to the touch panel itself.
In recent years, in-cell touch panels that are built into the cell of the display panel and the like have been developed in order to have a thinner and lighter weight device, to improve visibility, and to attain decreased costs resulting from a decrease in the number of parts due to the touch panel being provided in-cell.
A representative example of a configuration of an in-cell touch panel involves a structure in which so-called sensor electrodes, which are position detection electrodes that detect the position of contact of an object, are provided between an array substrate such as a TFT (thin film transistor) substrate and an opposite substrate such as a CF (color filter) substrate, which constitute an electrooptical device such as a display panel or a display device.
In general, sensor electrodes are light-transmissive electrodes made of ITO (indium tin oxide) or the like. In order to make the detection of a position of contact possible, the touch panel is provided with light-transmissive electrode patterns that extend in the column direction and light-transmissive electrode patterns that extend in the row direction, intersecting with the column direction electrode patterns.
However, transmittance and reflectance differ between regions where the light-transmissive electrode patterns are formed and where the light-transmissive electrode patterns are not formed, and thus, there is a problem that the light-transmissive electrode patterns are visible.
Patent Document 1 discloses a configuration in which dummy patterns made of a light-transmissive film having an index of refraction equal to that of ITO is provided in the gaps between the first and second light-transmissive electrode patterns (sensor electrodes) made of ITO. The configuration of Patent Document 1 narrows the area where none of the first light-transmissive electrode patterns, second light-transmissive electrode patterns, and dummy patterns are present, which causes the first and second light-transmissive electrode patterns to not be easily seen.